A QLED (Quantum Dots Light-Emitting Diode), like an OLED (Organic Light-Emitting Diode), can emit light on its own and has advantages of rapid response rate, wide viewing angle, lightweight, low power consumption and so forth. Since it has higher color purity, it can achieve wider color gamut when applied in a display device. Ligands on a surface of a quantum dot material can be modified and a quantum dot material is easily soluble in many solvents. Quantum dot materials thus are very suitable for low-cost solution processing techniques.
As a commercially used hole-injection-layer material, PEDOT:PSS is widely used in solution processed QLEDs so that the QLEDs can have excellent properties. However, PEDOT:PSS has a PH value between 1 and 3 at normal temperature, showing an acidic characteristic.
According to relevant researches, the acidic PEDOT:PSS may result in an unstable anodic interface, and thus reduce the life span of a diode. The main reason is as follows. The In2O3 (Indium (III) oxide) component of ITO (Indium Tin Oxide) may dissolve in an acidic environment, which results in that indium of ITO migrates to PEDOT:PSS, thus increasing the hole injection barrier. If indium spreads to a quantum dots light-emitting layer, it may result in the quenching of excitons and thus the efficiency and the life span of the diode will be reduced greatly.